ABB RELION 670 SERIES REG670 Applications Manual page 158

Section 7
Differential protection
152
shown in the right-hand side in figure 56) in order to put 110 kV & 36.75 kV currents
in phase.
To ensure proper application of the IED for this power transformer it is necessary to do
the following:
1. Check that HV CTs are connected to 1 A CT inputs in the IED.
2. Check that LV CTs are connected to 5 A CT inputs in the IED.
3. When delta connected CTs are used make sure that both CT sets are identically
connected (that is, either both DAC or both DAB).
4. For wye connected CTs make sure how they are 'star'red (that is, grounded) towards
or away from the protected transformer.
5. Enter the following settings for all three CT input channels used for the HV side
CTs, see table 20.
Table 20: CT input channels used for the HV side CTs
Setting parameter
CTprim
CTsec
CT_WyePoint
To compensate for delta connected CTs, see equation 16.
6. Enter the following settings for all three CT input channels used for the LV side CTs
Table 21: CT input channels used for the LV side CTs
Setting parameter
CTprim
CTsec
CT_WyePoint
Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062
Selected value for both solution 1
(wye connected CTs)
200
1
FromObject
Selected value for both Solution 1
(wye connected)
500
5
ToObject
1MRK 502 071-UUS A
Selected value for both Solution 2
(delta connected CTs)
200
=
115
3
(Equation 16)
EQUATION1891 V1 EN-US
1
ToObject
Selected value for both Solution 2
(delta connected)
500
=
289
3
(Equation 17)
EQUATION1892 V1 EN-US
5
ToObject
Application manual